Not applicable.
Not applicable.
This invention relates to an end milling cutter for machining workpieces made of a non-ferrous metal or plastic.
End milling cutters the machining portion of which comprises helically shaped cutting edges with helically shaped chip flutes therebetween are generally known. It is also known to provide so-called roughing cutters with a chip splitter profile in which the tool flank is interrupted by parallel-extending flutes.
In machining workpieces made of a non-ferrous metal or plastic, it is desirable to provide a large positive rake angle and a large positive clearance angle and a relatively small tool wedge angle (having a sharp profile), at the same time. The tool flank usually is on a spiral as viewed in a section. If a large rake angle and a large clearance angle are aimed at, which results in a wedge angle of from 40 to 60xc2x0, for example, this will impair the stability of the milling cutter. Therefore, a compromise has to be made between the stability of the milling cutter, on one hand, and the desired cutting characteristics, on the other.
It is the object of the invention to provide an end milling cutter for machining workpieces made of a non-ferrous metal or plastic wherein optimum rake and clearance angles are obtained while the stability of the milling tool is improved.
In the inventive end milling cutter, the tool flank or the back between adjacent chip flutes is facet-shaped such that it is composed of individual reference surfaces which are approximately planar, as viewed in a circumferential direction, and are disposed at an angle with respect to each other.
The inventive end milling cutter allows for a very small wedge angle, an optimum rake angle and clearance angle while the stability of the milling cutter tool portion remains sufficient. This also makes it possible to achieve high metal-cutting depths if the edge lengths of the end milling cutter are large enough.
Three or more reference surfaces are provided in an aspect of the invention. It is understood that the number of reference surfaces, their length in a circumferential direction of the end milling cutter, and the clearance angle determines the stability of the end milling cutter. However, the number of three or more reference surfaces which may be of approximately the same length is considered to be sufficient. Because of the invention, the chip flutes may be made to be very deep with no adverse effect exerted on stability. Large chip flutes are known to have a good chip-removing performance.
The angles which enclose the reference surfaces with respect to each other may be equal. However, it is also possible to choose differing angles. The rake angle in the front portion is preferably from 20 to 25xc2x0.
The inventive end milling cutter is preferably made of a high-speed steel or hard cutting metal. It goes without saying that the inventive milling cutter is not only suited for use as a finishing cutter, but also as a roughing cutter with a chip splitter profile as is known as such.
The invention will now be explained in more detail with reference to an embodiment thereof.